1. Field of the Invention
This invention relates generally to a valve actuating apparatus for engines, and more particularly concerns a system for actuating and controlling reciprocating valves for the cylinders of an internal combustion engine.
2. Description of Related Art
Conventional piston type internal combustion engines typically utilize mechanically driven camshafts for operation of intake and exhaust valves, with fixed valve lift and return timing and duration. Electrically or hydraulically controlled valves for improved control of valve operation have also been used in order to improve fuel economy and reduce exhaust emissions.
For example, a variable engine valve control system is known in which each of the reciprocating intake or exhaust valves is hydraulically controlled, and includes a piston receiving fluid pressure acting on surfaces at both ends of the piston. One end of the piston is connected to a source of high pressure hydraulic fluid, while the other end of the piston can be connected to a source of high pressure hydraulic fluid or a source of low pressure hydraulic fluid, under the control of a rotary hydraulic distributor coupled with solenoid valves.
Another engine valve actuating system is known in which each cylinder is provided with a coaxial venturi shaped duct having inwardly facing vanes that hold an electro-mechanical valve actuator. When the electro-mechanical valve actuator receives a pulsed electrical signal, the actuator operates to reciprocate the valve.
While a camshaft driven intake or exhaust valve will typically open and close with a constant period as measured in crankshaft degrees, for any given engine load or rpm, there is a need for an indirect valve actuation system for internal combustion engines that can operate more rapidly, and that will open the valve at the same rate regardless of engine operating conditions. Ideally, a valve actuation system should match the optimum, maximum valve rate of operation at maximum speed of operation of an engine to provide a rapid, optimum valve operation rate. It would also be desirable to provide a valve actuation system for internal combustion engines offering a speed of operation that will allow greater flexibility in programming valve events, resulting in improved low speed torque, lower emissions, and better fuel economy. Conventional approaches to providing higher rates of valve opening and closing have used non-latching control valves commonly involving systems using either spool valves or poppet valves, neither of which provide for a high flow open area in a small, low inertia system or energy efficient latching mechanisms. It would be desirable to provide a valve actuation and control system with an electro-hydraulic valve system, having a high flow open area, low inertia of operation, a small size, and case of manufacture. The present invention meets these needs.